Just Biology
by Sailboaty
Summary: The scientific discovery of genes predicting "good quirks" and "bad quirks" have set the stage for segregation and political tension. During an UA reunion party, Bakugo and Kirishima silently discover that genetics don't always lead to seperation, but powerful attraction. (An oneshot interpretation of ABO in BnHA.)


**Just Biology**

 _Prologue_

It became a time when having quirks was no longer special and those without quirks were rare finds, praised as purebred humans free of mutations. With more and more threatening quirks showing up in infirmaries minutes after birth, and children maturing their powers earlier and earlier due to scientific advancements, there was vocal demand for legalization and even criminalization of certain quirks. The world was just not ready for a population of special snowflakes with real weaponizable power. The topic of genetic screening and forced termination of births of humans with undesirable quirks was also heavily discussed and everyone had an opinion.

Amidst the legal deliberations between government quirk regulation and the protection individuality and human rights, a cultural revolution was also happening. In the interests of protecting the quirkless purebreds, Japanese media started to categorize practicing heroes as either 'alpha' or 'omega,' based on the threat levels of the quirk. Those with powers productive to the protection of purebreds were alphas, and those with counterproductive quirks were omegas. This categorization spread quickly among netizens and the popularity of these terms invited some scientists to eventually prove that there was a genetic difference between the alphas and the omegas. But, research into behavioral differences was slow due to difficulties in study recruitment.

No one knew the definitive differences between the two groups, and what the alpha and omega meant to each other.

Midoriya has been missing for the past year after his public protest of the genetic segregation of heroes. To the disappointment of his friends and family, he was forced into hiding after receiving demands from extremist groups to undergo full genetic screening before his words were taken seriously.

 _Story_

"Hey Bakugo! Nice seeing you here!"

"What do you want?"

It was the UA reunion reception, 5 years after their highschool graduation. It was nice, as UA always goes all out for festivities seen from the numerous fansigns to the decadent tablecloth. Yet Midoriya's absence and the talk of quirk segregation made everyone uneasy. Bakugo was especially uneasy, as the person he grew up with was on the run and it was difficult for him to find his relevance in a social setting without Deku to scream at. But now Kirishima was here, here and loud.

"Oh, I didn't expect you to be here." Kirishima scratched the back of his head, with his tailored suit making it a little difficult for him to raise his arms to his embarrassment.

"Oh, really. And why is that." Bakugo shouted back, not really wanting to partake in the small talk. Kirishima dropped his arm and transferred his gaze onto the ground, as if in reaction to the clouded atmosphere of the reunion party. Kirishima was revered as an alpha, due to his protective hardening quirk. Bakugo was labelled an omega due to his explosive quirk of only enabling violence and destruction.

"I didn't mean it like that, I mean all alumni are welcome at UA, it is UA, regardless if you are omeg—"

"What the fuck Eiji." Bakugo was shocked at the assumption, "I just fucking hate parties, but I just came thinking maybe that guy would show up. What is your problem, you are not seriously drinking the Kool-Aid piss by media right?"

Kirishima noticed the mistake in his assumption. It has been too long since Bakugo and he have seen eachother, and Kirishima has been working in the public eye for too long. The man's life was now dictated by hero rankings and public opinion, whereas Bakugo to everyone's surprise went to pursue higher education in America. He was always a smart one though, Kirishima remembers.

"Oy, Bakugo, no I am sorry. I…wanted to see Midoriya too." Kirishima didn't realize it immediately, but he pointed out the elephant in the room and he drew some attention with turned heads at the mention of Midoriya.

"Fuck off." Bakugo marched past Kirishima and pushed him roughly aside with his shoulder. Kirishima took it without hardening for defense, as he felt he deserved it -but he did not deserve Bakugo leaving him like that.

"Stop." Kirishima twisted around and placed his hand on Bakugo's shoulder. Bakugo rolled his neck to shrug him off, but Kirishima just slide down the smooth sleeve Bakugo's suit jacket to firmly grasp his friend's wrist.

Bakugo figured couldn't break free without causing a scene and intently stared back into the red eyes of the aptly named Red Riot in protest. He kept quiet, but his anger was felt through the tension of his wrist. His gaze challenged Kirishima to speak.

"Look. I am sorry. I didn't mean anything like that, we're equals." Kirishima fumbled his words, but he felt a surge of confidence as he felt the warmth of Bakugo's roughened skin against his bare palms. He felt like he had all the right to lecture him. And he had all the right to keep him there.

Equals? Bakugo was enraged at that assumption too, no one was his equal, he was at the top and unrivalled. Especially with Midoriya absent. He knew it. But what enraged him the most was that he felt no one longer believed it, no matter how well he performed, he was labelled as an inferior and a nuisance by the opinions of small-minded people who only looked at a few DNA sequences to determine a hero's worth. But in this moment, he was frustratingly unable to contest Kirishima, physically unable to as his body suddenly lost vigor. He felt drugged with foreign sensation.

"Ah." Bakugo heard himself agreeing in a beaten voice.

Kirishima felt strange too, as he heard himself affirm, "Good."

Suddenly, Kirishima's red eyes lit up, not by any friendship glitter but by flashes of light from where Bakugo's hand was held. Bakugo had activated his quirk in the middle of the reunion reception to break free of Kirishima's grasp. Although unexpected, Kirishima was able to harden in time to prevent his arm from being blown to pieces. The sleeve of Bakugo's grey suit was seared black, and the smoke residue shrouded his exit from the party through the parking garage doors. Before he made a clean break however, Kirishima caught a glimpse of the runaway's face -it wasn't a face of anger, but of panic.

If the two men did not draw enough attention already, most of the room was now looking in their direction. Audible whispers stirred, with several remarks about the distaste for omegas mixing with the few concerns by former classmates who closely predicted what had happened.

The parking garage's cool air washed over the nervous sweat coating Bakugo's forehead. Bakugo felt that he was going to puke. Was he drugged? He has never felt such involuntary feelings, with the closest being to when he forced Shinso to demonstrate his quirk on him in efforts to build up tolerance to the submission. But this time, even the blast from his explosive quirk was not able to snap him out of it. He was not one to submit, ever, even if it meant causing a scene, or even losing an arm, it is just how it is. Bakugo raced down the stairs of the parking garage, noticing the immobility his slacks caused as they were more constricting than his hero uniform. Or maybe it wasn't the pants, but the weakness in his legs. He had no choice but to sit himself down on the steps of the stairs and wait for the feelings to subside.

It was enough time for Kirishima to find him.

"What the hell Bakugo. You could've killed me."

"Well, I didn't." Bakugo was covered in sweat by now, and Kirishima almost didn't approach him due to the threat of him turning into a literal sweat bomb and blowing up the whole building.

"Are you avoiding me? I was looking forwards to seeing you again you know? It has been half a decade since you went overseas. I am sorry the hero scene in Japan…isn't what it used to be anymore. But it doesn't change who we are. Science is stupid. What's in the heart matters more right?" Kirishima punched the left side of his chest for expected emphasis and plopped himself down a few steps above Bakugo to give him space.

"I am not avoiding you because of this political bullshit Kirishima. Plus, science is not stupid. You and I are different. I don't want it to be real, but I know it probably is. I fucking feel it in my blood. I feel it, actively. Physically."

Kirishima didn't know what he was going on about, but his body knew. He was not like Bakugo, and Bakugo was not like him. Not inferior by any means, but different. "Well everyone is different right? But you can always change it I guess." Kirishima laughed as he toyed with the black roots of his damaged red hair.

"Some things can't be changed. People don't change. For example, no matter how hard I fight, it is preprogrammed into me to be destructive and inferior. Unlike people like Deku, and even you. Just fuck off."

"I don't think so."

The bold rejection struck a chord with Bakugo and he felt his temper dampened. It was as if cold water replaced the boiling sweat soaked through his shirt. Instincts again took over and he had no choice but to listen. Quietly. He didn't have enough firepower to blow the way out of this one. Kirishima skidded down some stair steps to join Bakugo on the lower level, hooking an arm around the human sweat bomb's neck as if in a headlock.

"It is ok to be who you are too you know, body and mind, one part doesn't have to be in control of the other, it is just, well, the whole human. And every part of you has a natural role in making you happy and you, you."

Bakugo looked up at Kirishima, he wanted to correct him that it was stupid to reduce a human to the mind and body and call him out on his weirdass inspirational speech, but he couldn't. Natural or not, Bakugo was aware of what he wanted, he just knew the consequences were high.

"I can't be your friend anymore."

"I really don't want to be your friend either sometimes." Kirishima laughed and tightened his grip on Bakugo, drawing him in with enthusiasm. Bakugo found himself letting him, without resistance.

"Ok, then let's not be friends." Now that he was up close with Kirishima, Bakugo could also feel the heat and sweat emanating off the man's body as if Kirishima was fighting against the same compulsions for the last hour. He felt the hand grasping his shoulder tense and release in a twitchy motion and he let out a sigh. Idiot. Bakugo groaned with irritation as he trailed his eyes along Kirishima's visibly tightening pants up to his face with a stare that seemed to dig far into the back of his target's mind.

"Sorry, I—" Kirishima released Bakugo immediately with dread. His body had betrayed the unassuming public demeanor he worked hard to maintain over the years in service and left him feeling exposed and grotesque in front of his best friend. Clutching his face to bring it down between his legs, Kirishima tried to conceal the flush and involuntary shivering he was desperately suppressing.

Bakugo stood up and tossed his burnt suit jacket down the stairs and began to unbutton his equally ruined dress shirt in annoyance. "It is fine." Kirishima peered up from his hands to watch Bakugo as he prepared to leave, exploring the options and excuses he had in his arsenal to save their friendship. But he couldn't think critically, overwhelmed by inexplicable emotions with a one-track mind of making Bakugo stay, he couldn't allow for him to leave again.

"I can't help it, you know?" Kirishima muttered between staggered breaths as he heaved his struggling body up from the ground.

"Then don't."

"Alright." Without much delay, Kirishima forcefully grabbed Bakugo by the waist and threw him back down on the stairs. Bakugo grunted as his back hit the stair's edges but did not complain as Kirishima looked on. "I don't want to hurt you."

"What part of me looks weak?" Bakugo glared up at the mess of guilt Kirishima was reduced to and confronted him with furrowed brows.

"That's not what I—"

"Just do it. It is not like you can possibly hurt me." Bakugo threw his charred shirt over Kirishima's face and then grabbed the crown of the man's head with assertion. "Just fuck me."

* * *

Written for my friend ET.


End file.
